Manual Wheelchair Propulsion Assist Devices

From ATWiki

Manual wheelchair propulsion assist devices can be retrofit to a user’s current wheelchair to enable them to propel themselves with less energy expenditure. There are three categories of propulsion assist devices: pushrim-activated power-assist wheels, wheelchair power drives, and mechanical advantage devices.

Introduction

A manual wheelchair is a very inefficient form of transportation[1]. Use of a manual wheelchair requires significant upper extremity strength, especially to traverse up or down inclines and to propel for long distances. Additionally, using a wheelchair for an extended amount of time can cause chronic shoulder pain and injuries[2]. For some users, a power chair is required when lack of muscle strength or energy is present. However, power wheelchairs are very heavy and do not fold to allow for easy transportation in a vehicle; a chair lift attached to a vehicle is required for these types of wheelchairs. For this reason, many individuals, even those with strength deficiencies, prefer a manual wheelchair to a power chair because it can be easily transported in a vehicle without special equipment[3].

There exist a number of add-ons to manual wheelchairs that assist the user in propelling themselves, but still retain the ease of transport of the manual wheelchair.

Types of Propulsion Assist Devices

Pushrim-activated power-assist wheels

Pushrim-activated power-assist wheels have a motorized wheel hub, which provides power to the wheels by the user pushing on the rims. See more at the pushrim-activated power-assist wheels page.

Wheelchair power drives

A power drive consists of a control unit, a battery pack, and a drive unit; these components are all made to attach to a wheelchair the user already owns. There are two types of power drives to add on to a manual wheelchair: those for the user to control and those for the attendant to control.

User-controlled

Frank Mobility e-fix user-controlled power drive

This type of power drive transforms the manual wheelchair into a power wheelchair, but is easily removed for folding and stowing of the wheelchair. The drive unit is typically a motorized hub on each wheel, which is controlled with a joystick. The drive unit can be turned off or removed when the user desires to manually propel the chair. The add-on weight ranges from 50 to 70 pounds, including the battery, depending on the model. These systems typically add 1-3” of width onto the wheelchair, and have a range of 10-15 miles of battery use.
Commercially available models include Frank Mobility’s e-fix, Golden Motor, Yamaha JWI, and Decon e-drive.

Attendant-controlled

Tzora Sampson attendant-controlled power drive

The attendant-controlled power drive is made to assist an attendant in propelling a manual wheelchair. The drive unit is usually a motor connected to a heavy-duty wheel or set of wheels that attaches under the wheelchair and drives the wheelchair via the control unit. The power drive can be easily removed from the wheelchair when it is unneeded (e.g. for indoor use) and for folding and stowing the wheelchair. The add-on weight of this type of propulsion assist device ranges from 40 to 70 pounds, including the battery. The battery typically lasts for 6-16 miles of continuous use, and no width is added to the wheelchair since the unit attaches under the chair.
Commercially available models include Frank Mobility’s viamobil, Tzora Sampson, Decon e-walk, and Excel Click & Go.

Mechanical advantage devices

RioMobility Pivot, a lever system for wheelchair propulsion

For wheelchair users who do not want the significant added weight of a battery unit, there is a propulsion assist device that utilizes levers pumped forward and back to propel the wheelchair. This lever system uses a mechanical advantage to reduce the effort required for the same distance traveled. The add-on weight is 3-8 pounds and does not need to be removed in order to fold the chair, though it can easily be removed through the use of a snap-lock system.
Commercially available models include Nordigo, Wijit, RioMobility Pivot, and NuDrive.

MagicWheels

Additionally, there is one type of mechanical advantage device that allows the wheelchair user to change gears, similar to a bike. Changing the gear ratio allows fewer pushes for going up hills and easier to brake going down hills. This model is called MagicWheels.

The Rowheel is a wheel that permits the user to perform a rowing motion (pulling backward on the wheels) to propel the wheelchair forward, rather than the standard pushing forward for forward propulsion. This lessens the muscular strain on the anterior deltoid and triceps and instead uses the stronger back muscles and biceps for forward motion.